Since the new generation of microwave links and mobile relays operate in the 22 GHz range, more and more high stability microwave sources are required having low consumption and low cost while also being capable of being electronically tuned in frequency.
The means used in the prior art consist in using a solid state component such as a gallium arsenide field effect transistor (GaAs FET) which is stabilized by means of a dielectric resonator, with the frequency of the oscillator being adjusted by displacing a disk immediately above the resonator.
However, when operating at about 22 GHz or above, it is necessary to use GaAs FET chips. In order to avoid the chips deteriorating over time, a vacuum must be set up inside the housing and an inert gas then inserted therein. It will readily be understood that it then becomes practically impossible to perform any mechanical adjustment after the oscillator has been assembled in equipment, in particular when the frequency of the oscillator varies over time, whence the necessity of using an oscillator having a transistor and a dielectric resonator which are capable of being tuned in frequency using a varactor.
When it is desired to vary the frequency of an oscillator having a transistor and a dielectric resonator, or when it is desired to modulate said oscillator, one of the means used consists in coupling a stripline to the main transmission line and in inserting a varactor on the coupled line. The dielectric resonator may be placed between the two lines.
In this technology, adjustment of the dielectric resonator serves simultaneously;
to couple the varactor containing stripline to the main stripline;
to determine the frequency of the oscillator; and
to obtain optimum power output from the osoillator.
However, when operating at high frequencies, for example at about 22 GHz, an oscillator of this type becomes highly critical to implement and particularly difficult to adjust in mass production.
The object of the present invention is to mitigate these drawbacks.